Using FF 60.0.3 in Windows 10, I compared an older Prefs.js file with today's and noticed both changes and additions in the current copy. So, am looking for a strategy to place unchanging preferences and place them in a User.js file and leave the rest in the Prefs.js file.

Since I sync with the same FF version in Linux Mint where I may not have made a particular change, would the sync overwrite the Windows version with the Linux version?

Older, from when, from what version.You've got to figure that prefs can change between versions, certainly between different machines/OS.And there may not be any right or wrong answer at a particular time.

If you know that on every install or for every Profile that you use, you make particular pref changes, like to disable all updates, then something like that I would think to be worthwhile to include in a user.js. For changes that you regularly make.

But for other changes, that may vary depending on which way the wind is blowing, it might be worth understanding what they do, how they may affect things, & understanding that if the changes are from Mozilla, they have a reason for doing so. If said changes are counter to your wishes, stick those particular ones into user.js.

So compare the two prefs.js, try to understand what they diffs are & how they may have come about, but unless they are changes you specifically made, pretty much let things go at that.

therube, thanks for your comments. By older, I meant about 7 days old. I understood the differences of the changed Prefs and none of them would be included in a User.js. They are data updates and some 4 new Prefs installed by the browser. Also booted into Linux Mint and the sync does update the about:config settings. Changes I made previously in Windows was updated on Linux Mint as well. Luckily I use one profile only and aim to have identical setups in both OS.

My settings involve simple convenience changes, like do not close browser when last tab is closed, omit warning about redirect, and settings for a RAM cache.

If you do not want to sync preferences, turn off the setting to sync them in your Firefox Account settings.

Hamburger Menu -> Click on your name.

Once the options open to the sync settings, turn off the checkbox for Preferences, thought it may read "Options" now as mine does.

You may need to do that on each machine. Or, turn it off and then make sure you hit the sync button, but still check all the other connected devices.

My apologies if I am reading your question wrong, but to me it sounds like you want to be able to monkey with a setting on Linux and probably leave it alone on Windows, while having a master user.js file that you can share between the two when the mood strikes.

Give a man a fish, and he eats for a day. Teach a man to fish, and he eats for a lifetime.I like poetry, long walks on the beach and poking dead things with a stick.Please do not PM me for personal support. Keep posts here in the Forums instead and we all learn.

Thanks smsmith, Preferences are most important for me as I switch between Windows 10 and Linux Mint 19 while working on the same project. With both running FF (currently v64.0) I need the working environments to be the same. It wasn't a matter of me hacking the linux settings. There was a glitch in the sync logic algorhithm. This has happened before and my first thought was to know which components are being synced and is the Prefs.js included?